This invention relates to improved portable abrading tools, such as power driven sanders or the like.
The tools of the present invention are of a known general type in which a piston is reciprocated within a cylinder body by pressure fluid, usually compressed air, and acts to reciprocate a work abrading shoe relative to the body. In certain prior devices of this type, the piston has been provided with a toothed rack which engages and meshes with a gear unit rotatably mounted to the body of the device, with that gear unit also engaging a second rack connected to the abrading shoe to drive the shoe.
The prior devices of this type with which I am familiar have tended inherently to vibrate the body of the tool excessively in operation, with resultant discomfort in the user and difficulty of precise control of the positioning of the tool on the work. In addition, the rack and gear drives heretofore employed have been of a character tending to exert lateral or transverse force against the piston and/or the shoe, in a manner causing excessive wear of these parts and their bearing surfaces with respect to the body of the device, and particularly tending to cause excessive wear of the engaging piston and cylinder surfaces. Additionally, the valving for controlling flow of air or other pressurized fluid to opposite ends of the cylinder has been so ineffective and impositive in nature that the entire reciprocating motion frequently stops upon imposition of a fairly light manual force against the tool.